# G6 Host Bridge Runtime Contract Report

> Date: 2026-04-18
> Scope: `G6` minimum runtime contract implementation

## Summary

`G6` has moved from pure fail-closed classification to a minimum runnable runtime contract.

The implementation does not redesign the browser host transport. Instead it generates a conservative `host_bridge_workflow` script that:

1. preserves host bridge actions
2. preserves localhost host-runtime dependencies
3. lists callback business endpoints
4. invokes host bridge APIs when available
5. invokes callback endpoints through the existing browser request path
6. returns blocked/error/partial/ok artifact statuses instead of pretending full equivalence

## Assets Updated

1. `src/generated_scene/generator.rs`
2. `tests/scene_generator_test.rs`

## Contract

The minimal `G6` contract is now:

1. at least one `host_bridge` workflow step
2. at least one `callback_request` workflow step
3. at least one business endpoint

If that contract is missing, generation still fails closed.

## Validation

Executed:

```powershell
cargo test --test scene_generator_test g6 -- --nocapture
cargo test --test scene_generator_test -- --nocapture
cargo test --test scene_generator_p1_family_test -- --nocapture
cargo test --test scene_generator_family_policy_test -- --nocapture
cargo test --test scene_generator_canonical_test -- --nocapture
```

All target regressions passed.

## Result

`G6` now has a minimum generated package path while retaining a fail-closed negative test for incomplete contracts.

The next runtime-contract target is `G7 multi_endpoint_inventory`.